The degree to which bile acids are conjugated with taurine probably depends upon the availability of taurine to the liver. The object of this project is to determine what aspects of taurine metabolism in man influence the availability of taurine for bile acid conjugation and to what extent taurine in extra-hepatic pools is available for bile acid conjugation. For the most part we shall study patients with predictable abnormalities of taurine metabolism (patients with obstructive jaundice, biliary drainage, ileal resection or on cholestyramine therapy) to de- termine what measurements correlate best with taurine-loaded and taurine-depleted states. Using Dowex column separations, the amino acid analyzer, and other methods we shall measure plasma, muscle, and liver taurine concentrations, urinary taurine excretion, and bile acid glycine/taurine ratios (the latter as an index of pool size of available taurine). We shall supplement these data with in vivo and in vitro animal studies which will allow us to focus on selected aspects of taurine metabolism. We shall define the physical state of taurine in plasma, which, according to our preliminary data, is not all free. With this data base, we shall extend our studies to patient groups without abnormalities in bile salt metabolism but in whom abnormalities of taurine metabolism might be predicted. We shall study patients with chronic renal failure, who have little renal taurine excretion, to determine if they resemble patients with obstructive jaundice, who also lack one pathway for taurine excretion. We shall determine whether uremics with cholestyramine-responsive pruritis, have taurine overload as the first step in consideration of taurine as a pruritic factor in uremia and biliary obstruction. Study of fasting patients or patients on long-term parenteral hyperalimentation will indicate the degree to which endogenous taurine synthesis can supply taurine requirements in man in the absence of exogenous intake.